Tab-type partitions are well-known in the art, as typified by the following patents: Bower U.S. Pat. No. 456,353; Herr U.S. Pat. No. 529,173; Williams U.S. Pat. No. 533,331; Carter U.S. Pat. No. 1,143,036; Lorentzen U.S. Pat. No. 1,442,280; Burger U.S. Pat. No. 2,677,491; and the Raubenheimer U.S. Pat. Nos. 4,358,047 and 4,103,818. All of these patents had the problem of the difficulty of interlocking the partition strips and the bending down or crushing of the tabs as the partitions were interlocked by forcing the tabs across the blank space between the two openings.
It was known, as in the Herr patent and the Carter patent, that slits could be used to aid in engagement of the two partition strips together. However, the types of slits typified by Herr and Carter did not relieve the crushing force as the tabs were forced across the blank space between the openings. And the Raubenheimer patents did not have any such provision. Furthermore, the prior art did not show the present feature of providing spaced aligned hinging edges in each of the two openings, namely, the slot and the second opening, with a third the edge at the inner end of the slot displaced from the hinge line, to reduce the offset caused when the partitions are folded to flat position. Such offset is illustrated in FIG. 5 of the Herr patent. This offset tends to force the partitions apart lengthwise and thereby tends to remove the tabs of one partition strip from the opening of the other when the partitions are in relatively flat interlocked positions, and thereby to unlock them.
It has been found that if the two spaced hinging edges, one in each of the two openings, be maintained but that this intermediate edge at the inner end of the slot be displaced away from alignment with the two edges mentioned, the offset of the partitions as they are in relatively flat positions, is made less abrupt, and the unlocking tendency is reduced.
Thus the objects of the invention are to provide partitions of this type, each having a slot providing a tab, and a second opening, with a slit that makes the tab yieldable, and a slit that makes the blank space that the tab must pass across yieldable, to make engagement of the partition strips easier, and to reduce the crushing effect on the tabs, to make the inner edge of the tabs sloping to increase the distance across the slots which must receive the bridging portions between the slots and the openings. Also an object is to reduce the tendency of the offset of the partitions when in flat position, to separate the partitions, by making the offset less abrupt.